Area Overhead Research Articles

A Lightweight Power Side-Channel Attack Protection Technique With Minimized Overheads Using On-Demand Current Equalizer

A lightweight on-demand current equalizer is proposed in this brief to enhance the resistance of the encryption engine to power side-channel attack (PSCA) with a minimized performance-power-area (PPA) overhead. The proposed on-demand current equalizer is operated based on the real-time activity of the encryption engine to minimize the corresponding current signature leakage, while enhancing the supply quality by reducing the voltage droop. Therefore, an encryption engine employing the proposed PSCA protection technique has a low power overhead without suffering from any performance degradation. In addition, an embedded randomization method is proposed to further strengthen the resistance of the encryption engine to PSCA while maintaining the power supply quality. A prototype chip that integrates the proposed design, a 128-bit advanced encryption standard (AES) engine, and a digital low-dropout voltage regulator (DLDO) was fabricated in 180-nm CMOS technology. Measurement results show that the proposed design achieves <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$234{\times }$ </tex-math></inline-formula> minimum traces to disclose (MTD) improvements in correlation power analysis (CPA), with no performance overhead, 21.17% power overhead, and 32.88% area overhead, respectively.

A Comprehensive Evaluation of Integrated Circuits Side-Channel Resilience Utilizing Three-Independent-Gate Silicon Nanowire Field Effect Transistors-Based Current Mode Logic

Side-channel attack (SCA) is one of the physical attacks, which will reveal the confidential information from cryptographic circuits by statistically analyzing physical manifestations. Various circuit-level countermeasures have been proposed as fundamental solutions to eliminate the correlations between side-channel information and circuit’s internal operations. The existing solutions, however, will introduce nonnegligible power and area overheads, making them difficult to be deployed in resource-constrained applications. In this article, a novel three-independent-gate silicon nanowire field effect transistor (TIGFET) with the intrinsic SCA-resilience characteristics is introduced to balance the tradeoffs among cost, performance, and security of cryptographic implementations. We construct six TIGFET-based current mode logic (CML) gates that can retain lower power variation under all possible transitions compared to the CMOS counterparts. As a proof of concept, advanced encryption standard (AES), SM4 block cipher algorithm (SM4), and lightweight cryptographic algorithm PRESENT are implemented utilizing the TIGFET-based CML gates. Correlation power attack is performed to evaluate the improvement of SCA resilience. Simulation results verify that the TIGFET-based cryptographic implementations decrease 42.37% area usage, lower 61.16% energy efficiency, reduce <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5.35\times $ </tex-math></inline-formula> power variation, and achieve a similar level of SCA resistance compared to the CMOS counterpart, which is applicable for the resource-constrained applications.

Stop and Look: A Novel Checkpointing and Debugging Flow for FPGAs

Hardware checkpointing enables live migration, fault recovery, and context switching, but has been difficult to achieve for FPGA applications. We detail techniques to checkpoint complex FPGA designs and develop StateMover, a new checkpoint-based debugging flow for FPGAs that combines the speed of hardware execution with the full observability and controllability of simulation. StateMover can safely stop a running design and seamlessly move its state back and forth between an FPGA and a simulator. StateMover can create complete design checkpoints even for designs that have multi-cycle I/O interfaces, contain buried state that is not accessible by FPGA readback, and use external memories. StateMover and its associated IPs allow a designer to quickly make a design checkpointable, with a small area overhead. Moving the state from/to an FPGA to/from a simulator can be performed in a few seconds for large Xilinx UltraScale FPGAs.

Fully-Integrated Switched-Capacitor Converter With Capacitor Bridging for Improved Current Density

A 6-phase, 3 interleaving cells bridged, fully-integrated 1/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times $ </tex-math></inline-formula> switched-capacitor converter (SCC) is proposed. Two techniques, called capacitor bridging and phase expansion, are proposed and implemented in this SCC to solve the idling capacitor problem and reduce area overhead. The phase clamp technique is also proposed to solve the drain and source flipping issue. This brief was designed in 65 nm CMOS technology, and measurement results show that the current density is improved by 25% comparing to the traditional 3-phase 1/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times $ </tex-math></inline-formula> SCC without sacrificing efficiency.

Field programmable gate array implementation of an adaptive filtering based noise reduction and enhanced compression technique for healthcare applications

AbstractNowadays, the development of e‐health monitoring devices is getting more demand for remote health applications. In addition, cardiovascular diseases is considered the most chronic disease in recent years. So, this requires a fast diagnosis and therapy to clear this issue and requires an information transformation from the patient to the distant hospital. But, it faces many challenges like more energy consumption, data security, storage, and transmission. In addition, the electrocardiogram (ECG) data must be processed in real‐time, and the information must have high predictability and lossless compression. So, in this article, an enhanced set partitioning in hierarchical tree decoder with deep belief neural network is developed for ECG compression. Due to an inappropriate channel in telemedicine applications, the ECG signals transmitted through a wireless network are affected by noise. So, fast normalized least mean square (FNLMS) algorithm based adaptive filter is deliberated to eliminate the unwanted noise from the ECG signal. Also, the structure of the FNLMs based adaptive filter is modified by developing a systolic structure to increase the speed of filtering process. Moreover, the parallel and pipelined architecture is provided for the proposed compression unit to reduce the processing time and the area overhead as compared to the existing methods. A publicly available database called the MIT‐BIH database and real‐time ECG data records are used for simulation purposes. The proposed design was implemented on the Xilinx platform and the MATLAB tool. The performance of the proposed design is estimated by the parameters like compression ratio, signal to noise ratio, root mean square error, and percentage root mean square difference (PRD), PRD normalized, and quality‐score. It is compared with existing designs to show the efficiency of our proposed design.

A sub-threshold 10T FinFET SRAM cell design for low-power applications

This paper presents a high-stability low-power 10 T (HSLP10T) sub-threshold SRAM cell with single-ended operations. The HSLP10T cell uses a decoupled read path, formed by a transmission gate and a dynamic inverter, thereby, resulting in read stability improvement. In addition, it employs a feedback-cutting transistor to facilitate the write operation, which increases writability. Due to single-ended operations, direct-write on complementary node, floated bitline, and use of more p-type transistors, the power consumption reduces in the proposed cell. Simulated results in the 7-nm FinFET technology indicate that at a 300 mV supply voltage, the read stability/writability of the proposed HSLP10T cell is 2.06X/1.31X as that of the conventional 6 T cell. Moreover, the dynamic/leakage power consumption is reduced by 1.82X/2.92X when compared with the conventional 6 T SRAM. The proposed HSLP10T SRAM bitcell has a layout area of 0.047 µm2, which is 1.67 × larger than the conventional 6 T SRAM. However, the highest ON-to-OFF currents ratio related to the proposed design compensates for this area overhead by connecting more number of cells to the same bitline in the columns of the SRAM array. Moreover, the minimum operation voltage is reduced by 48.28 % using proposed design compared to the conventional 6 T SRAM.

Design of Light-Weight Timing Error Detection and Correction Circuits for Energy-Efficient Near-Threshold Voltage Operation

Near-threshold voltage (NTV) operation has the potential to improve the energy efficiency of digital integrated circuits. However, the use of a conservative timing guard band to avoid the timing errors introduces excessive timing margins, thus causing larger energy dissipation in the NTV region. An error-tolerant design based on timing error detection and correction circuits has been shown to be a promising solution to mitigate these issues. This paper presents a light-weight timing error-tolerant flip-flop (ETFF) design. This design detects timing errors using a node transition signal detector with only nine transistors and corrects these errors during the same clock cycle. Moreover, transistor sizing is explored to optimize the trade-off between performance and area overhead. The proposed ETFFs are inserted into a monitored circuit by replacing original flip-flops at timing-monitored points. To further reduce the overhead, we develop a mean-time-to-failure-aware method to select the monitored points by simultaneously considering the critical path coverage and activation rates of flip-flops. The simulation results show that a CNN accelerator using the proposed timing error-tolerant design implemented in the SMIC CMOS 40 nm process can robustly work at 1.1–0.3 V with only 3.5% area overhead. Furthermore, this design reduces the area overhead by 54.68% and improves the energy efficiency by 53.69% at 0.6 V, compared with the Razor flip-flop design. The advantage of the proposed design lies in that it requires smaller circuit overheads and can work reliably in a wider range of supply voltages.

Time- and Amplitude-Controlled Power Noise Generator against SPA Attacks for FPGA-Based IoT Devices

Power noise generation for masking power traces is a powerful countermeasure against Simple Power Analysis (SPA), and it has also been used against Differential Power Analysis (DPA) or Correlation Power Analysis (CPA) in the case of cryptographic circuits. This technique makes use of power consumption generators as basic modules, which are usually based on ring oscillators when implemented on FPGAs. These modules can be used to generate power noise and to also extract digital signatures through the power side channel for Intellectual Property (IP) protection purposes. In this paper, a new power consumption generator, named Xored High Consuming Module (XHCM), is proposed. XHCM improves, when compared to others proposals in the literature, the amount of current consumption per LUT when implemented on FPGAs. Experimental results show that these modules can achieve current increments in the range from 2.4 mA (with only 16 LUTs on Artix-7 devices with a power consumption density of 0.75 mW/LUT when using a single HCM) to 11.1 mA (with 67 LUTs when using 8 XHCMs, with a power consumption density of 0.83 mW/LUT). Moreover, a version controlled by Pulse-Width Modulation (PWM) has been developed, named PWM-XHCM, which is, as XHCM, suitable for power watermarking. In order to build countermeasures against SPA attacks, a multi-level XHCM (ML-XHCM) is also presented, which is capable of generating different power consumption levels with minimal area overhead (27 six-input LUTS for generating 16 different amplitude levels on Artix-7 devices). Finally, a randomized version, named RML-XHCM, has also been developed using two True Random Number Generators (TRNGs) to generate current consumption peaks with random amplitudes at random times. RML-XHCM requires less than 150 LUTs on Artix-7 devices. Taking into account these characteristics, two main contributions have been carried out in this article: first, XHCM and PWM-XHCM provide an efficient power consumption generator for extracting digital signatures through the power side channel, and on the other hand, ML-XHCM and RML-XHCM are powerful tools for the protection of processing units against SPA attacks in IoT devices implemented on FPGAs.

Local bit-line shared pass-gate 8T SRAM based energy efficient and reliable In-Memory Computing architecture

The In-Memory Computing (IMC) architecture based on Conventional 6T, 8T, and 10T SRAM suffers from compute disturbance, compute-failure, and half-select issues, which affect the reliability of In-Memory Boolean Computation (IMBC) operations. To overcome these problems, local bit-line Shared pass-gate Dual-Port 8T (SDP8T) SRAM-based IMC architecture is proposed to perform energy-efficient IMBC operations. The local bit-line shared pass-gate structure addresses the half select issues with a small area overhead and achieves higher array efficiency by incorporating the bit-interleave architecture. The virtual-VSS write-assist is used in SDP8T SRAM to improve the write-margin yield (μ−3σ) by 48.99%, and multi-VTH technique improves Decoupled Read-Margin (DRM) yield by 5.26% when compared to DP8T SRAM. The Dynamical Reset Word Line (DRWL) scheme is proposed to resolve the sneak current problem and make the proposed IMC architecture more resilient to compute disturbance at non-read decouple paths during IMBC operations. Further, the Reference-based Reconfigurable Sense Amplifier (RRCSA) scheme is proposed to achieve reliable (compute-failure free) sensing for IMBC on four operands simultaneously in a single cycle, normal read, and Binary Content Addressable Memory (BCAM) operations. The 4 Kb SRAM array is implemented in 65-nm CMOS technology to analyze the SDP8T-IMC architecture. The operating frequency of 1190 MHz and average-energy consumption of 18.56 fJ/bit are achieved during IMBC operation at 1V. For BCAM operations, it achieves 0.60 fJ/search/bit energy consumption in the worst case (i.e., all data mismatch) at 1V. Cumulatively, the proposed SDP8T-IMC architecture has the highest figure of merits than the recently reported IMC architecture.

Reliable Circuit Design Using a Fast Incremental-Based Gate Sizing Under Process Variation

As CMOS devices become smaller, aging-induced and process variations become major issues for circuit reliability. In this paper, a statistical gate sizing method is proposed to improve the lifetime reliability of manufactured chips in the presence of process variations and aging effects. To this end, we propose a canonical first order delay model to estimate the delay degradation of a gate under negative bias temperature instability and process variations considering spatial correlations. Using the proposed gate delay model, a statistical static timing analysis method is introduced to compute the circuit delay considering the joint effect of process variation and negative bias temperature instability. To guarantee that the circuit meets the required timing constraints, we propose an incremental gate sizing technique. This technique first computes the criticality of each gate defined as the probability that a gate lies on the critical path due to negative bias temperature instability and process variations. Then, a group of gates with the highest ranking according to criticality is chosen for a gate sizing-based timing optimization. It is worth nothing that, by using the proposed statistical gate delay model, we can compute the criticality of each gate incrementally. Experimental results based on ISCAS’85 benchmark circuits show that the proposed method can improve the lifetime reliability defined as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.1(\mu + 3\sigma)$ </tex-math></inline-formula> of the initial delay distribution of the circuit at the expense of 8.64% area overhead. In comparison with the path-based method, the proposed approach is much faster, especially for larger circuits, which makes it a viable solution to optimize the lifetime reliability of very large-scale circuits used in industry.

High-Speed Post-Quantum Cryptoprocessor Based on RISC-V Architecture for IoT

Public-key plays a significant role in today’s communication over the network. However, current state-of-the-art public-key encryption (PKE) schemes are too complex to be efficiently employed in resource-constrained devices. Moreover, they are vulnerable to quantum attacks and soon will not have the required security. In the last decade, lattice-based cryptography has been a progenitor platform of the post-quantum cryptography (PQC) due to its lower complexity, which makes it more suitable for Internet of Things applications. In this article, we propose an efficient implementation of the binary learning with errors over ring (Ring-BinLWE) on the reduced instruction set computer-five (RISC-V) platform. Our field-programmable gate array (FPGA) implementations improve the speed of scheme operations by more than 51% in terms of CPU cycles compared to previous work. The proposed hardware module has low complexity and only imposes around 6%–9% overhead to the original core. Moreover, it has constant-time operations and is resistant to timing attacks. Besides, a more reliable fault-resilient variant of the architecture with 1% area overhead is proposed. According to the application-specific integrated circuits (ASICs) implementations, the proposed architecture achieves at least 32%, 79%, and 50% lower power, energy, and area consumption compared to the previous work, respectively.

A High Performance SIKE Accelerator With High Frequency and Low Area-Time Product

Post-quantum cryptography (PQC) has emerged as a quantum-resilient class of cryptography that will be able to withstand attacks from quantum computers. Among the PQC family, the isogeny-based scheme, i.e., Supersingular Isogeny Key Encapsulation (SIKE) protocol, an alternative candidate in Round 3 of the National Institute of Standards and Technology (NIST), has the advantage of a shorter public-key length. However, longer computational time and larger area overhead are the main constraints for its practical applications. In this brief, we proposed a SIKE accelerator with optimized multiplier and adder designs achieving the lowest area-time (AT) product with high operating frequency. The proposed SIKE accelerator for four different security levels has the highest frequency of 303.0-322.5 MHz with 4.0-21.0% improved AT in comparison to the state-of-the-art designs.

A Compact Single-Ended Inverter-Based Transceiver With Swing Improvement for Short-Reach Links

This paper presents a compact single-ended inverter-based transceiver with swing improvement for short-reach links. The low output impedance of the transmitter enlarges the output swing and the eye size to overcome large single-ended noise while relaxed impedance matching provides good signal integrity. For good area efficiency, the proposed transmitter utilizes an inverter driver which is much smaller than the conventional source-series termination driver and thus occupies only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$42.5 ~\mu \text{m}^{2}$ </tex-math></inline-formula> . By taking the advantage of a large signal swing, the receiver consists of only four slicers and latches to minimize area overhead and to simplify the design. The transceiver was fabricated in 28-nm CMOS technology and tested at supply voltage of 1.13 V. The transmitter achieved a large output swing of 850 mV, which is 50.4 % larger than the conventional source-series termination transmitter. At the far-end of a channel consisting of a 1 m SMA cable and a 17 mm printed circuit board trace, the transmitter achieved eye openings of 440 mV and 234 mV at 16 Gb/s (−2.7 dB) and 20 Gb/s (−8 dB), respectively. Even with a large switching noise of 100 mV, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-situ</i> eye at the receiver was measured 114 mV with 7.4 dB loss.

PROLEAD

Even today, Side-Channel Analysis attacks pose a serious threat to the security of cryptographic implementations fabricated with low-power and nanoscale feature technologies. Fortunately, the masking countermeasures offer reliable protection against such attacks based on simple security assumptions. However, the practical application of masking to a cryptographic algorithm is not trivial, and the designer may overlook possible security flaws, especially when masking a complex circuit. Moreover, abstract models like probing security allow formal verification tools to evaluate masked implementations. However, this is computationally too expensive when dealing with circuits that are not based on composable gadgets. Unfortunately, using composable gadgets comes at some area overhead. As a result, such tools can only evaluate subcircuits, not their compositions, which can become the Achilles’ heel of such masked implementations.In this work, we apply logic simulations to evaluate the security of masked implementations which are not necessarily based on composable gadgets. We developed PROLEAD, an automated tool analyzing the statistical independence of simulated intermediates probed by a robust probing adversary. Compared to the state of the art, our approach (1) does not require any power model as only the state of a gate-level netlist is simulated, (2) can handle masked full cipher implementations, and (3) can detect flaws related to the combined occurrence of glitches and transitions as well as higher-order multivariate leakages. With PROLEAD, we can evaluate masked mplementations that are too complex for existing formal verification tools while being in line with the robust probing model. Through PROLEAD, we have detected security flaws in several publicly-available masked implementations, which have been claimed to be robust probing secure.

An efficient and energy-aware design of a novel nano-scale reversible adder using a quantum-based platform

Quantum-dot cellular automata (QCA) is a domain coupling nano-technology that has drawn significant attention for less power consumption, area, and design overhead. It is able to achieve a high speed over the CMOS technology. Recently, the tendency to design reversible circuits has been expanding because of the reduction in energy dissipation. Hence, the QCA is a crucial candidate for reversible circuits in nano-technology. On the other hand, the addition operator is also considered one of the primary operations in digital and analog circuits due to its wide applications in digital signal processing and computer arithmetic operations. Accordingly, full-adders have become popular and extensively solve mathematical problems more efficiently and faster. They are one of the essential fundamental circuits in most digital processing circuits. Therefore, this article first suggests a novel reversible block called the RF-adder block. Then, an effective reversible adder design is proposed using the recommended reversible RF-adder block. The QCAPro and QCADesigner 2.0.3 tools were employed to assess the effectiveness of the suggested reversible full-adder. The outcomes of energy dissipation for the proposed circuit compared to the best previous structure at three different tunneling energy levels indicate a reduction in the power consumption by 45.55%, 38.82%, and 34.62%, respectively.

Digitally Assisted Mixed-Signal Circuit Security

The design and manufacturing steps of a chip typically involve several parties. For example, a chip may comprise several third-party intellectual property (IP) cores and the integrated circuit (IC) fabrication may be outsourced to a third-party foundry. IP cores and ICs are shared with potentially untrusted third parties and, as a result, are subject to piracy attacks. Even more, any legally purchased chip may be reverse engineered to retrieve the design down to transistor level and, thereby, it is also subject to piracy attacks. In this article, we propose <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MixLock</i> , an anti-piracy countermeasure for mixed-signal IP cores and ICs. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MixLock</i> protection is based on inserting a lock mechanism into the design such that correct functionality is established only after applying a key which is the designer’s secret. The lock mechanism acts on the mixed-signal performances by leveraging logic locking of the digital part. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MixLock</i> presents several key attributes. It is generally applicable, it is nonintrusive to the sensitive analog section, it incurs no performance penalty and has very low area and power overheads, it is fully automated, and it is capable of co-optimizing security in both the analog and digital domains. We demonstrate <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MixLock</i> on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Sigma \Delta $ </tex-math></inline-formula> analog-to-digital converter (ADC) using hardware measurements and an audio demonstrator.

Quantum Tunneling Based Ultra-Compact and Energy Efficient Spiking Neuron Enables Hardware SNN

Low-power and low-area neurons are essential for hardware implementation of large-scale SNNs. Various novel-physics-based leaky-integrate-and-fire (LIF) neuron architectures have been proposed with low power and area, but are not compatible with CMOS technology to enable brain scale implementation of SNN. In this paper, for the first time, we demonstrate hardware implementation of recurrent SNN using proposed low-power, low-area, and low-leakage band-to-band-tunneling (BTBT) based neurons. A low-power thresholding circuit is proposed. We further propose a predistortion technique to linearize a nonlinear neuron without any area and power overhead. We establish the equivalence of the proposed neuron with the ideal LIF neuron to demonstrate its versatility. The tunneling regime enables a high input impedance in the BTBT neurons (few <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{G}\Omega$ </tex-math></inline-formula> ) to enable a voltage input without loading the synaptic array. To verify the effect of the proposed neuron, a 36-neuron recurrent SNN is fabricated in GF-45nm PDSOI technology. We achieved 5000x lower energy-per-spike at a similar area and 10x lower standby power at a similar area and energy-per-spike. Such overall performance improvement enables brain scale computing.

Digital Fault-based Built-in Self-test and Evaluation of Low Dropout Voltage Regulators

With increasing pressure to obtain near-zero defect rates, there is a need to explore built-in self-test and other non-traditional test techniques for embedded mixed-signal components, such as PLLs, power converters, and data converters. This article presents an extremely low-cost built-in self-test technique for LDOs, specifically designed for fault detection. The methodology relies on exciting the LDO loop at the voltage reference input via a pseudo-random signal with white noise characteristics and observing the response from the output of LDO via all-digital circuitry, thereby inducing low area and performance overhead. The BIST circuit along with an LDO as a device under test is designed in 65nm technology. Fault simulations performed at the transistor level show that all resistive open/short defects in circuit components can be detected even if they do not cause a catastrophic failure in the LDO response. The proposed technique is validated with hardware using off-the-shelf components.

An improved reconfigurable logic in resistive random access memory

Emerging non-volatile devices have shown great potential in computing in-memory (CIM). This work proposes a logic design method based on the complementary resistance switching (CRS) structure, which is connected by two anti-serially memristors. Three logics including AND, OR, and NIMP can be implemented in one step. Moreover, XOR logic can be implemented in two steps. Based on the proposed design, a 1-bit full adder is implemented with the fewer number of memristors and operation steps compared with existing works. The feasibility and correctness of our design are verified by the SPICE simulations with the Voltage Threshold Adaptive Memristor (VTEAM) model. In addition, we evaluate the ISCAS’85 benchmark circuit based on the proposed logic. Compared with existing methods, the performance and area overhead have been improved by the proposed method.

Small-Signal Processing Low-Overhead Operational Amplifier for delta-Sigma ADC

Aiming at the fully differential (FD) sensing and high-precision small-signal output characteristics of micro-electromechanical systems (MEMS) gyroscopes, a low area overhead, high-gain, medium-speed, FD operation amplifier (Op-Amp) is designed for building a small-signal processing delta-Sigma analog-to-digital converter (ADC). The Op-Amp is a two-stage cascade structure, which combines folded cascade (FC) and gain-boosted technology to make the low frequency gain up to 129 dB, to meet the high-precision requirements of 18-bit delta-Sigma ADC. The first stage is FC gain-boosted structure, which uses a small bias current to achieve high-gain and low area overhead. In order to reduce the input noise, process smaller signals, the input pair adopts positive channel Metal–Oxide–Semiconductor (PMOS). The second-stage uses a large bias current to achieve a high unity gain bandwidth (UGB). Under the premise that the tail current source of the first stage is PMOS, in order to reduce the area overhead, abandoning the traditional common source (CS) structure of negative channel Metal–Oxide–Semiconductor (NMOS) input and PMOS as the current mirror load, adopting a new CS structure that PMOS input and NMOS used as independent bias current source. In this structure, the large overdrive voltage significantly reduces the size of transistors and greatly reduces the area overhead. The Op-Amp was implemented in SMIC 0.18 μm BCD process, 5 V supply voltage. Its post-layout simulation achieved a low-frequency gain of 129 dB, a UGB of 35 MHz and a phase margin (PM) of 62° for a load capacitance of 2 pF. Output voltage swings are ±3.71 V and including common mode feedback (CMFB), bias voltage generating circuit and filter capacitor, the area of Op-Amp is 167.162 μm × 200.82 μm. Behavioral-level verification shows that the designed Op-Amp meets the requirements of high-precision delta-Sigma ADCs.